A digital receiver typically includes an analog front-end and a digital circuit part. The analog front-end typically includes a radio frequency (RF) tuner, which converts an radio frequency (RF) signal down to a baseband signal, filters the signal, and makes appropriate power adjustment to remove out-band signal power and ensure the signal amplitude is at a suitable level.
In the digital receiver, the analog baseband signal output from the radio frequency (RF) tuner is sampled and quantified by an Analog Digital Converter (ADC) to generate digital signals for processing by the digital circuit part of the digital receiver. The digital receiver may perform various processing tasks, such as digital filtering, sample rate conversion, symbol timing synchronization, carrier synchronization, frame synchronization and forward error correction, etc., to recover the data from the received signal.
In a typical digital receiver for Second Generation Satellite Digital Video Broadcasting (DVB-S2), the spectrum inversion status is decided by a Forward Error Correction (FEC) module, which calculates the Bit Error Rate (BER) and determines whether the spectrum inversion has occurred based on the calculated Bit Error Rate (BER). For example, if the Bit Error Rate (BER) is outside a reasonable range, the spectrum can be considered to be inverted; otherwise, the spectrum can be considered to be not inverted. When the spectrum is inverted, the time period for the digital receiver to reach a locked working state will be quite long.